<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>16 执行环境栈</title>
	</head>
	<body>
		<script type="text/javascript">
			// 执行环境栈:其实就是一个出栈和压栈的过程
			var a = 1;
			var b = 2;
			function fn(x) {
				var a = 10;
				function bar(x) {
					var a = 100;
					b = x + a;
					return b;
				}
				bar(20);
				bar(200);
			}
			fn(0);
			console.log(a,b);
		</script>
	</body>
</html>
